This invention relates generally to touch sensitive systems, and more particularly to identifying a location of a touch on a touch sensitive system that uses bending-wave touch sensors.
Touch panels are used to provide two-dimensional coordinate information. One example may be an opaque track pad while another example may be a transparent touchscreen placed in front of a display such as a liquid crystal display. Touch panels may be based on a variety of touch technologies including four-wire and five-wire resistive, capacitive, infrared and surface acoustic wave types, as well as bending-wave touch technologies.
In one approach, bending wave touch systems may detect a touch based on a tap of an object, such as a key or finger, used to excite bending waves in a substrate. These bending waves induce electrical signals in piezoelectric elements or sensors (piezos) bonded to the substrate. These signals are captured by electronics and processed to determine a set of (X,Y) coordinates of the touch position, such as by using time-of-flight methods to extract touch coordinate information from piezo signals.
Unfortunately, noise in the environment can cause problems, for smaller sensor sizes, such as those used in handheld applications and point-of-sale. Ambient noise may be detected by the touchscreen system as a false touch or series of false touches, causing confusion while actively using the touchscreen and/or by erroneously selecting options displayed on the screen. For example, in some applications, brief moments of corrupted signal data can be a major problem due to generation of false touch coordinates.
There remains a need for improved acoustic fingerprints and matching algorithms, as well as improved identification of corrupted signal data, for use in bending-wave touch systems.